Wound dressing tapes intended for application to wounds that exude bodily fluids should prevent the introduction of bacteria or other pathogens into the wound while permitting maximum evaporation of exuded fluids. At the same time, such tapes should also provide good initial adhesion--in order to prevent premature release of the tape--and minimal build-up of adhesion--so as to minimize skin trauma upon removal of the tape.
Commercially available wound dressing tapes typically include either a rubber-based or an acrylic-based adhesive with acrylic-based adhesives generally favored because of their hypoallergenic nature.
While the hypoallergenic nature of an adhesive is one factor to be considered in assessing acceptability of the adhesive for use in a wound dressing tape, traumatization of skin upon removal of a wound dressing tape is primarily correlated to changes in the cohesion of skin cells resulting from prolonged coverage of the skin with an occlusive tape or bandage. The type and severity of skin injury resulting from the removal of many conventional wound dressing tapes varies with the length of time the tape is worn. The longer a tape is worn, the more hydrated and thus macerated the outer layer of the stratum corneum becomes. The internal strength of the stratum corneum can be significantly reduced when macerated in this manner, resulting in deep and irregular fractures within the stratum corneum upon removal of a wound dressing tape. When occlusive medical tape is worn for short intervals of time--such as a few minutes--the upper layer of the stratum corneum will not gain significant fluid from the underlying skin layers and the tape can be removed without significant trauma to the skin. However, when occlusive medical tape is worn on the skin for prolonged periods--such as twenty four hours--fluids will build-up in the upper layers of the stratum corneum and frequently result in severe skin fractures upon removal of the tape.
Trauma to the skin can be lessened when the wound dressing tape permits evaporation of fluids from underneath the tape. This fact has led to the development and sale of wound dressing tapes which provide a high moisture vapor transmission rate.
Potter (U.S. Pat. No. 4,595,001) discloses formation of a moisture vapor transmissive wound dressing tape by pattern coating an adhesive onto a backing so as to leave a significant percentage of the backing in direct contact with the skin.
Rawlings (U.S. Pat. No. 4,798,201) discloses formation of a porous, moisture vapor permeable adhesive film for use in a wound dressing which is formed by coating a mixture of an emulsion adhesive and petroleum spirits onto a silicone release liner or backing film.
Takermoto (European Patent Application Publication 0 353 972) discloses formation of a moisture vapor transmissive wound dressing tape by dot coating an adhesive onto a backing so as to leave a significant percentage of the backing available for direct contact with the skin.
Silver (U.S. Pat. No. 3,691,140) discloses formation of a porous, moisture vapor permeable adhesive film for use in a wound dressing which is formed by solvent coating a swelled solid microsphere adhesive onto a backing at a coating weight effective for permitting particle to particle discontinuities to form between microspheres in the adhesive layer as the swelled microspheres shrink due to evaporation of the solvent.
These tapes advantageously maintain a relatively normal moisture content of the outermost skin layers so that any fractures in the skin caused by removal of the wound dressing tape will develop near the surface of the naturally desquamating layers of the stratum corneum. However, such tapes tend to lack sufficient initial adhesion to the skin and frequently fall off. In addition, such tapes typically exhibit significant build-up of adhesion which counteracts the reduced trauma benefit achieved from the enhanced breathability of the tape.
In summary, the prior art offers a choice between aggressive adhesive tapes which result in significant injury to the skin upon removal and minimally aggressive adhesive tapes that allow for moisture transmission but are prone to premature release from the skin. Consumer preference has resulted in most conventional adhesive tapes using the minimally aggressive adhesives.
Hence, a substantial need exists for a moisture vapor transmissive, low trauma wound dressing tape exhibiting good initial adhesion and minimal build-up of adhesion.